OISD STD-150

Design and Safety Requirements�for Liquefied Petroleum Gas Mounded Storage Facility.
This standard lays down minimum requirements on safety, design, layout, installation, operation, maintenance and testing of aboveground fully mounded bulk vessels used for storage of Liquefied Petroleum Gas (LPG) installed in the refineries, gas processing plants, terminals, bottling plants and auto LPG dispensing stations.

1. OISD-STD-150
DESIGN AND SAFETY REQUIREMENTS
FOR LIQUEFIED PETROLEUM GAS
MOUNDED STORAGE FACILITY
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2. CONTENT
■Introduction
■Scope
■Definitions
■Location and Safety Distances
■Mounded LPG Storage Facilities
■Fittings and Instrumentation on aVessel
■Electrical Area Classification
■Fire Detection / Protection System
■Operation, Maintenance and Inspection
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3. INTRODUCTION
■Liquefied Petroleum Gas (LPG) handling has many challenges due to its inherent
dangerous properties.
■The conventional method of storage of LPG in India is in a pressurized vessel installed
aboveground.
■The mounded storage of LPG eliminates the possibility of Boiling Liquid Expanding
VapourExplosion(BLEVE) has proved to be safer compared to above ground storage
vessels.
■The area of land required to locate a mounded system is minimal compared to
conventional storage.
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4. SCOPE
■This standard lays down minimum requirements on safety, design, layout, installation,
operation, maintenance and testing of aboveground fully mounded bulk vessels used for
storage of Liquefied Petroleum Gas (LPG) installed in the refineries, gas processing
plants, terminals, bottling plants and auto LPG dispensing stations.
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5. DEFINITIONS
■Mounded Vessel(s)
–Astoragevessel(s)sitedabovegroundandcompletelycoveredbyamoundofearthor
similarinertmaterialexceptfornozzles,manholecovers,inspectioncoversfittedon
Vessel(s).
■Bullet
–Ahorizontalpressurevesselusedforstorageortransportationbyrail/road.
■KerbWall
–Awallofappropriateheightandsizeconstructedofsuitablematerialanddesignedto
containtheLPGspillageandtodirectittoasafelocationaroundthestoragevessel.
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6. DEFINITIONS
■Purging
–Itistheactofreplacingtheatmospherewithinaequipmentbyaninertgas/LPGvapourin
suchamannerastopreventtheformationofexplosivemixture.
■SMPV (Unfired) Rules.
–TheseareRulesgoverningthestorage,transportation;handlingetc.ofcompressedgasin
vesselsexceeding1000litersinvolume.TheserulesareframedundertheIndianExplosives
Act,1884andadministeredbyChiefControllerofExplosives.
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7. LOCATION
■The Mounded area should be free of disturbances.
■Proper Space for the movement of construction/fabrication equipment and materials is
ensured properly.
■Analysis of soil testing is vital for the foundation of mounded LPG vessels.
■The manhole and safety relief valves of mounded vessels shall be in a well-ventilated
position.
■Fire hydrants/ monitors shall be positioned at a safe distance.
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8. SEPARATION DISTANCES
■The key parameters which are to be noted in the Separation distances of LPG Vessels:
•Between vessels and other buildings –15 m
•Between vessels and Fire water Pump house –30 m
•Between vessels and other facility –15 m
■A road of minimum 3.5 m width shall be provided around the mound for movement of
earth moving / fire fighting equipment.
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10. MOUNDED LPG STORAGE FACILITIES
STORAGE VESSEL(S)
–Horizontallyplacedcylindricalvessel(s)shallbeusedformoundedstorage.
–DesignCode:ASMESEC.VIIIorPD-5500orequivalentdulyapprovedby
CCE.Asinglecodeshallbeadoptedfordesign,fabrication,inspectionandtesting.
–Thespecificconsiderationshallbegivento
•Internalvapourandhydraulicpressure
•Externalloadingsonthevessel
•Internalvacuum
–MaterialSelection:Itshouldbedesignedasperdesigncode.
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11. STORAGE VESSEL(S)
–Themechanicaldesignofstoragevesselforrefineryserviceare:
•Materialshallbeinlinewithdesigncode.ASTMA516Gr.60oreqv.shallbe
used.
•Micro-alloyedsteelcontainingNi,Mo,Vashallnotbeconsidered.
•Maximumspecifiedtensilestressshallnotbemorethan80,000psi.
–ForMarketingInstallation:WhereH2Sisnotpresent,ASTMA516Gr.70(IT)or
SA537Cll(IT)orPD:5500oreqv.materialshallbeused.
–DesignTemperature:-27degCto+55degC.
–DesignPressure:14.5Kg/cm2g
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12. STORAGE VESSEL(S)
–InternalCorrosionAllowance:1.5mm(minimum)&Radiography:Full
–Thedimensionsofthevesselshallbedecidedbasedonsiteconditions,soil
mechanics,typeoffabricationfacilitiesavailableandotherdesignconsiderations.
–SurfacecoatingsandCathodicprotectionmethodsareusedtoprotecttheexternal
surfaceofthevessel.
–Thecathodicallyprotectedsystemshallbeisolatedfromtheunprotected
structures/surfacesbyinstallingmonolithicjoints
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13. MOUNDED LPG STORAGE FACILITIES
MOUND
–Vesselshallbeplacedonafirmfoundation&installedsoastopreventmovement
orflotation.
–Subsoilwater,rainwateroranyothersurfacewaterpercolationshouldnotbe
allowedintothemound.
–1:200longitudinalslopetobeprovidedtofacilitatedrainage.
–Adequateelevationofsandbed(Min.760mm)requiredtofacilitatedrainagefrom
LPGliquidoutletpipebygravity.
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15. MOUND
–MoundingMaterial–Compactedsandofminimumthicknessof700mm&Non
Combustiblemateriallikevermiculateorperlite.
–Imperviouslayerslikegeo-textilelayersontop&bottomofvesselstominimize
ingressofmoistureintothemoundandinturntocheckcorrosionofvessel.
–Protectivecoveringwithprefabricatedstonetilesoropenconcretetilestoprotect
earthcoverfromrainorwind.
–Topsandcoveronthevesselsshallbemin.700mm.
–Moundsurfaceshallbeprotectedbyprovidingprotectivecoverorprefabricated
stone,openconcretetilesetc.
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16. FITTINGS AND INSTRUMENTS ON A VESSEL
■Allthefittings/instrumentsshallbesuitableforuseatnotlessthanthedesignpressure
ofthevesselandforthetemperaturesappropriatetotheworstoperatingconditions.
■TheROVshallbeprovidedonfirstflangeonliquidline(s)fromthevesseleitherfrom
bottomortop.
■Liquidoutlet-topofthevessel-thelineshallextenduptobottom.
■Liquidline-bottomofthevessel-theminimumdistanceof3mfromthevesselto
ROVshallbemaintained.
■Thenozzlepipe-slopeofminimum-1.5deg.
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17. FITTINGS AND INSTRUMENTS ON A VESSEL
■Minimumtwonos.ofmanholeshallbeprovidedontopofthevessel.
■Eachvesselshallhaveat-leasttwoSafetyReliefValves(SRV).Thefullflowcapacityof
eachSRVonmoundedvessel(s)shallbeminimum30%ofthecapacityrequiredforan
equivalentsizeofabovegroundvessel.SRVsshallhavelockopen(orcarsealopen)
typeisolationvalvesonbothsidesofSRV.
■ThedischargeofSRVsshallbeconnectedtoflaresystemwhereveravailable
■Theflangejointsofvalvesshalleitherhavespiralwoundmetallicgasketsorringjoints.
Plainasbestossheet/reinforcedgasketsshallnotbeused.
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18. FITTINGS AND INSTRUMENTS ON A VESSEL
■Eachstoragevesselshallhaveminimumtwodifferenttypesoflevelindicatorsandone
independenthighlevelswitch.Highlevelalarmshallbesetatnotmorethan85%level
ofthevolumetriccapacityofthevessel.Audiovisualindicationshallbeprovidedatlocal
panel&controlroom.
■Eachvesselshallalsobeprovidedwithonepressureandtemperaturemeasuring
instrument.Thepressuregaugeshallbeprovidedwithtwoisolationvalvesandan
excessflowcheckvalve.Incase,temperaturegaugeprovidedonthevesselisinthermo
well,itshallbeweldedtovessel.
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19. HAZARDOUS AREA CLASSIFICATION
■ThehazardousareashallbeclassifiedasperIS:5572andOISD-STD-113.The
electricalfittings/equipmentintherespectiveclassifiedarea/zoneshallbeofatype
suitablefortheparticulararea/zoneasperclassificationinlinewithIS:5571.
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20. FIRE DETECTION / PROTECTION SYSTEM
■AUTO FIRE DETECTION / PROTECTION SYSTEM
–Automaticfiredetectionand/orprotection(Fixed)systembasedonheatdetection
throughthermalfuses/quartzbulbs/EPdetectorsshallbeprovided.Sensorsshall
beinstalledatallcriticalplacesasbelow:
•MinimumOnedetectorshallbeprovidedoneachexposedportionofthe
vessel.However,ifthenozzlesarecoveredinadome,eachgroupshallhaveat
leasttwodetectors.
•AtleastonedetectorshallbeprovidednearROVonallliquidline(s).
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21. AUTO FIRE DETECTION / PROTECTION SYSTEM
–An audiovisual alarm at the local/ main control panel and fire water station,
indicating the fire.
–All ROVs on the affected vessel shall close.
–LPG pumps and compressors in LPG storage area shall trip.
–Sprinklers. If provided, shall operate.
–In addition, devices for initiating all the above actions shall be provided on remote
operating panel and also in field at safe location to enable manual actuation.
Suitable arrangement for routine testing of security system shall be provided.
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22. FIRE DETECTION / PROTECTION SYSTEM
■GAS DETECTION SYSTEM
–Suitable gas detectors shall be placed at critical locations in the LPG storage area
such as near the ROVs, in inspection tunnel, inside the nozzle box enclosure (if
provided) or dome connection, near water draining/ sampling points.
–Audio-visual alarms showing the location of gas leakage shall be provided on the
control panel. First level alarm shall be set at 20% of Lower Explosive Limit (LEL)
and second level alarm at 60 % of LEL.
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23. FIRE DETECTION / PROTECTION SYSTEM
■WATER REQUIRMENT/ STORAGE
–The mound of vessel (s) provides protection against direct flame impingement and
minimisesheat absorption from nearby fires. Therefore, for water requirement /
storage in mounded storage area, the clauses of OISD -STD –144 w.r.t. medium
velocity water sprinklers shall not be applicable.
–The fire proofing ( 2 Hours rating) of all exposed portion of the vessel shall be
done including piping uptothe first ROV, appurtenances etc. Alternatively, auto
actuated fixed water spray system shall be provided and this system should be
actuated through heat detection device installed.
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24. FIRE DETECTION / PROTECTION SYSTEM
■Hydrant (s) / monitor (s) coverage shall be provided for adequate coverage of
unprotected portions exposed to thermal radiation including the top of the mound and
product pipelines. It shall be located at a safe place and shall not be installed within 15
meters from the exposed portion facilities/equipment to be protected.
■Measures to prevent the freezing of cooling water supplies and frost damage to supply
lines etc. shall be provided in the areas where heavy snowfall can be expected.
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25. OPERATION, MAINTENANCE AND
INSPECTION
■SafetyReliefvalvesshallbetestedandcalibratedeveryyearbyacompetentperson.
■PSPreadingsatfeedingpointsshallbemonitoredfortnightly.Insulatingjointsand
couplingsshallbeinspectedonceinayear.
■Thesettlementofthevesselshallbemonitoredatleastonhalfyearlybasis.
■Vessel(s)shallbesubjectedtohydrotestonceevery10yearsorateveryweldingtothe
vessel(repairsornewconnections)whicheverisearlier,byacompetentperson.
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26. OPERATION, MAINTENANCE AND
INSPECTION
■Vesselsshallbetestedevery5yearsinternallyusingvisualtechniquesanditswall
thicknessshallbemeasuredultrasonically.
■Themoundcoverofthevesselshouldbedulyinvestigated.
■Anyrepairsormodificationsshallbecarriedoutonlyaftertakingapprovalfrom
applicableauthority
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